i should be forewarned, i love energy drinks. >> do you really? >> but a new government survey finds that 20 thourk people went to the e.r. after downing energy drinks in 2011, twice as many as four years earlier. abc's lisa stark put herself to the test to show why. >> reporter: on youtube, downing these energy drinks is a game. lots of fun. >> on your mark, get set, go. >> reporter: but this new government study calls consumption of energy drinks a rising public health problem. of those 20,000 e.r. visits in 2011, 42% had mixed the energy drink with another stimulant like ritalin or with alcohol. but 58% reportedly used energy drinks alone. so what might be going on to send someone to the e.r.? >> blood pressure goes up, heart rate goes up and they'll start to feel the effects. heart racing, heart skipping. panic attack symptoms. irregular heart rhythms. panic attacks. >> reporter: caffeine is a drug. the most popular drug in the world. you can feel and see the effects on the body. i downed the equivalent of about four cups. doctors took a look